1. Field of the Invention
The present invention relates to display device such as a thin film transistor (TFT) array panel and a fabricating method thereof.
2. Description of the Related Art
In a liquid crystal display (LCD), an LCD panel comprises a TFT array panel, a color filter array panel, and liquid crystal sandwiched between the TFT array panel and the color filter array panel. For reference, the LCD panel cannot emit light for itself, so that there is additionally needed a backlight unit. Here, the backlight unit is located behind the TFT array panel and emits light toward the TFT array panel. Further, the transmittance of the light emitted from the backlight unit is adjusted depending on the molecular alignment of the liquid crystal.
Consumer demand for an LCD having a wide screen, high definition and a high aperture ratio has been increasing. As the side of LCD displays increases, the length of the wiring of the LCD is increasing, while the width thereof is decreasing. As a result, resistance values for LCD wiring are increasing. This may result in increased RC delay, which in turn may lead to distortion of displayed images.
Metals such as chrome (Cr), molybdenum-tungsten alloy (MoW) or the like, which have relatively high resistivities (e.g., 10 μΩ/cm or more), are commonly used for the wiring material. However, the resistivity of these materials may be prohibitively high for wide-screened LCDs having a size of 20 inch or more. Accordingly, large screen LCDs may require wiring materials having relatively low resistivity.
Examples of lower resistivity materials include silver (Ag), copper (Cu), aluminum (Al), etc. Among these metals, silver and copper have poor adhesion properties with respect to the glass substrate materials used for TFT array panels. Copper and amorphous silicon (which may be used for a semiconductor layer of a TFT) may inter-diffuse, thereby damaging the TFT and lowering the resisitivity of the copper.
Because of shortcomings of silver and copper such as those described above, aluminum is generally used as basic material for the wiring. Aluminum has many merits such as a low resisitivity (about 3 μΩ/cm), ease of wire formation, low-cost, etc.
However, aluminum has weak corrosion-resistance to chemicals, so that it can be easily oxidized or short-circuited. To make up for the weak corrosion resistance, a double layer aluminum/molybdenum structure may be used, incorporating a molybdenum upper layer. Molybdenum may be used due to its strong corrosion-resistance to the chemicals.
However, a hillock may be formed when forming a double layer aluminum/molybdenum structure.